Seeding implements typically comprise a frame adapted for travel over the ground, a plurality of furrow opener assemblies attached to the frame to open one or more furrows, and a distribution system for depositing agricultural materials such as seed and fertilizer into the furrows.
The furrow opener assemblies vary widely in design, but an important object of any design is to maintain the depth of the furrow as constant as possible, such that seed placement is at a constant depth to ensure uniform plant emergence as nearly as possible. The actual furrow opening element will be a hoe or knife type that essentially drags through the soil to form the furrow, or a disc opener comprising a disc which rolls through the soil at an angle to the travel direction to form the furrow.
Disc assemblies may be double disc openers with two discs oriented at an angle such that the discs converge and meet at a lower forward point of the discs to cut the suil at that point, and then diverge rearward of the contact point to form the furrow. A tube is located to drop seed and fertilizer between the discs and into the furrow.
Disc assemblies may also be single disc openers where a single disc engages the soil at an angle to the travel direction, such that a leading face of the disc pushes soil toward one side, such that seed and fertilizer can be deposited into the furrow by a tube adjacent to the trailing face of the disc.
Depth control on disc openers can be accomplished by providing a gauge wheel adjacent to the leading face of the disc. For example, U.S. Pat. No. 4,331,205 to Sorenson et al. discloses a double disc opener with a gauge wheel adjacent to each disc. The gauge wheels can be moved closer to the disc where it is desired to clean wet soil from the disc face, or farther away from the disc as desired. U.S. Pat. No. 4,760,806 to Bigbee discloses a single disc opener with a gauge wheel adjacent to the leading face of the disc. In Bigbee the gauge wheel actually rotates in contact with the leading side of the disc to clean the disc.
A downward bias force is exerted on the furrow opener assembly to force the discs down into the ground to a depth where the gauge wheel contacts the ground and prevents the disc from going any deeper. Such a gauge wheel provides very accurate depth control, since the gauge wheel rolls very close to the disc. Such gauge wheels also have disadvantages in some conditions.
With the gauge wheel close to the disc, the disc is very sensitive to lumps of soil or crop residue in the field. When the gauge wheel rolls up and over an obstruction, the disc also moves up an equal distance, causing uneven seeding depth in conditions of heavy trash or uneven field conditions.
Soil conditions vary across a field and it is necessary to provide sufficient downward force to penetrate harder field areas. In field areas where the soil is soft, especially with a single disc opener this downward force on the gauge wheel can force the gauge wheel down into softer soils, making a furrow that is too deep. High downward forces on the gauge wheel can also lead to over compaction on the sidewall of the furrow in some conditions, and also pulverization of vulnerable soil leading to increased erosion. Soil moved by the disc to form the furrow can pile up in front of the gauge wheel and cause the gauge wheel to stop rotating and bulldoze the soil when excessive downward force on the gauge wheel prevents the gauge wheel from rolling up over this soil.
Each opener type has advantages and disadvantages. For example single disc openers are preferred where the soil is firm, such as in no-till seeding operations where the soil is not cultivated prior to seeding. Single disc openers penetrate the soil better, generally disturb the soil less, and also are less prone to “hair pinning,” a condition where straw and trash left on the soil surface are pushed down into the furrow. Double disc openers are preferred for softer soils, such as where the soil is cultivated prior to seeding.
Where the furrow is a seed furrow, once seed is deposited in the furrow it is generally desired to move soil back over the furrow and pack the soil on the furrow. Depending on the particular furrow opener assembly, soil may simply fall back into the furrow or a furrow closing means may be provided. Typically a packer wheel then rolls along the furrow to pack the soil.
In a common furrow opener assembly configured to maintain consistent seed depth, the front end of a trailing arm is pivotally attached to the seeder frame such that the arm extends generally rearward and downward from the frame and can pivot up and down with respect to the seeder frame. A packer wheel is then rotatably attached to support the rear end of the trailing arm. A furrow opener is attached to the trailing arm ahead of the packer wheel such that the vertical position of the bottom of the furrow opener with respect to the bottom of the packer wheel can be fixed at a desired location to substantially set the depth of the furrow. A bias element is provided to force the trailing arm downward to push the furrow opener into the soil and force the packer wheel again it the ground.
The packer wheel pushes down the soil over the seed in the furrow and the bottom of the packer wheel corresponds to the soil surface. The depth of the furrow is substantially determined by the vertical distance that the bottom end of the furrow opener extends below the bottom of the packer wheel. Such a trailing arm furrow opener assembly is disclosed for example in U.S. Pat. No. 7,159,523 to Bourgault et al., particularly in FIG. 1 thereof. U.S. Pat. No. 5,396,851 to Beaujot and U.S. Pat. No. 5,609,114 to Barton disclose trailing arm furrow opener assemblies that operate in a similar way.
A problem occurs with trailing arm furrow opener assemblies such as that of Bourgault, Barton, and Beaujot in uneven terrain where the distance between the frame and the ground varies. As the vertical distance of the frame above the ground varies the trailing arm moves up and down about its pivotal attachment to the frame and the angle of the trailing arm changes such that the distance from the middle portion of the arm, where the furrow opener is attached, to the ground varies, and thus the actual depth of the seed furrow varies.
To improve the consistency of the furrow depth Bourgault et al. also disclose, in FIGS. 5-9 of U.S. Pat. No. 7,159,523, a trailing arm formed by upper and lower parallel arms connected at each end by front and rear links. Such a parallel link assembly has the property that the rear link is maintained in a constant horizontal and vertical orientation through the vertical range of motion without tilting forward or rearward. The front link thereof is fixed to the implement frame and the rear packer wheel and the furrow opener are fixed to the rear link. Thus as the packer wheel moves up and down relative to the frame in uneven terrain, the packer wheel and furrow opener move together vertically and so the furrow depth is maintained at a constant depth. Such a parallel arm however is very sensitive again to lumps of soil or crop residue in the field. Like the gauge wheel closely adjacent to the furrow opening disc described above, when the packer wheel in FIG. 5 of Bourgault moves up over a lump, the furrow opening element moves up the same amount causing uneven seed depth in lumpy field conditions.
U.S. Pat. No. 7,191,715 to Wendte et al. discloses a planting unit attached to a frame with a parallel link mechanism. The unit includes hoppers for carrying seed and fertilizer and a metering system to deliver this material to the furrow. Wendt discloses a double disc furrow opener assembly with a gauge wheel beside each disc and with a walking beam arrangement to reduce the sensitivity of the apparatus to lumps on the field. Each gauge wheel is mounted to the front end of a walking beam beside the discs, and a packer wheel is mounted to the rear end of each walking beam. Closer discs move soil back over the furrow in front of the packer wheels. The unit is supported on the walking beam at the mid-point of the walking beam. Thus when either the front gauge wheel or rear packer wheel rolls over a lump and moves up by the height of the lump, the mid point of the beam only moves up only one half of the height of the lump. Wendte also discloses that a swivel can be provided between the right and left rear packer wheels to further reduce movement of the furrow opening discs when the rear packer wheel rolls over a lump.
Similar walking beam planter units are disclosed in U.S. Pat. No. 5,351,635 to Hulicsko and U.S. Pat. No. 5,461,993 to Ikumoto et al. Also U.S. Pat. No. 4,750,441 to Pfenninger and U.S. Pat. No. 4,846,084 to Sigle disclose a furrow opener supported at the mid-point of a walking beam. The beam has wheels at its front and rear ends and the furrow opener is located between the front and rear wheels.